Fix FindwxWidgets on Ubuntu and Debian

When the Ubuntu package libwxgtk3-dev is not installed, FindwxWidgets succeeds even the required libraries are not actually found. The reason for that is that wx-config does not perform any kind of check and uses hardcoded values.

This affects e.g. KiCAD build process and makes it fail with a confusing error message: https://bugs.launchpad.net/kicad/+bug/1630020

Solution is to check for presence of every header and library file obtained from wx-config.

Topic-rename: FindwxWidgets-verify-wx-config

added 3 commits

• a38b3e8b - Do not end with fatal error when wxWidgets is not found
• f2b9dfa2 - Name _found variable properly
• be84482d - Check presence of the libraries sooner in order to get nicer error message

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added workflow:wip label

added 1 commit

• daadd0f8 - Prefix all variables with w_lib

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added 2 commits

• 4b674f88 - Use MATCHES syntax instead of regex replace
• 5bc536e5 - Use HNTS with find_library

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added 1 commit

• 27ed744b - Use HINTS with find_library

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resolved all discussions

@yaqwsx thanks for the updates. Please squash this all down to one commit and force-push the branch.

added 1 commit

• d4594825 - Fix FindwxWidgets on Ubuntu and Debian

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assigned to @brad.king

changed milestone to %3.9.0

added 1 commit

• e8b77084 - FindwxWidgets: Verify existence of libraries reported by wx-config

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@yaqwsx thanks. I updated your branch once more to revise the commit message and tweak the logic slightly. Please fetch and reset your local checkout.

Do: stage